#include <cstring>
#include <iostream>
using namespace std;

string a, b;
int n;
int index(string a_, string b_)
{
    int sum = 0;
    int i = n, j = 6;
    int p = 0;
    int temp = 0;
    if (j > n)
        return 0;
    while (temp = (a_.find(b_, p)) != -1)
    {
        sum++;
        p = j + temp;
    }
    return sum;
}
int main()
{
    cin >> n;
    cin >> a;
    b = "sdu120";
    cout << index(a, b) << endl;
    return 0;
}